This invention relates to apparatus for the homogenisation of liquids such as emulsions and dispersions.
In a known form of apparatus of the type to which the invention relates, the liquid which has to be homogenised, which may be a mixture of liquids, is jetted towards the edge of a blade and over the blade. As the liquid passes over the blade it is mechanically worked upon whereby the homogenisation of the liquid takes place. It is not entirely clear exactly what happens to cause the homogenisation of the liquid impinging upon the blade, but in some cases the blade vibrates at ultrasonic frequency due to the impingement of the liquid and the vibration of the blade exercises an agitating effect on the liquid assisting in the homogenising process. Moreover, the vibration creates cavitation at the blade surface which also assists in the homogenisation process.
Because of the aforesaid vibration of the blade, such known apparatus is often referred to as a liquid whistle.
There is another belief that the vibration of the blade does not add significantly to the homogenisation of the liquid, but that it is the cavitation which is the principal factor in the effectiveness of the homogenising process.
In any event, in the known apparatus, the blade is located in a cavity from which the liquid, after striking the blade, is drained off and the known apparatus, whilst it has proved to be extremely useful, is somewhat limited as to its adjustability, especially when in use, and frequently the apparatus are not run at best efficiency for the liquids being worked upon.
There has been one proposal for increasing the range of adjustability of the apparatus and this proposal is that the cavity in which the blade is located is caused to be filled in use and the pressure of the liquid in the cavity is controlled to an optimum by restricting the flow of liquid downstream of the cavity. This proposal suggests that by controlling the pressure of the liquid in the cavity the range of efficiency of the apparatus is increased and better homogenisation over a wider range of liquid types is achieved, and also that the apparatus can be adjusted to adjust the cavity pressure and the apparatus performance, whilst the apparatus is in use.